Purpose/Aim
MMC-HVDC is widely utilized in power transmission techniques. As one of the most critical components of MMC，accurate estimation for junction temperature of high voltage IGBT is significant for the reliable operation. Some of the existing utilized temperature sensitive electrical parameters (TSEPs) is difficult in real field application in terms of the low sensitivity and invasive implement. To address this issue, pre-turn-off current during turn-off is proposed to estimate the junction temperature of high voltage IGBTs.
Experimental/Modeling methods
The IGBT turn-off process is related to junction temperature due to excess carrier recombination. Thus, pre-turn-off current is defined as the current value at a fixed delay time from the moment of 90% load current is influenced by junction temperature as shown in Fig.1(a). To derive the relationship between the pre-turn-off current and bus voltage, load current and junction temperature, a half-bridge high voltage IGBT module (FF150R12ME3G) was selected to perform the double pulses test with hot plate.
Results/discussion
The results show that the pre-turn-off current is linear with junction temperature from Fig. 1(b). The temperature sensitivity ranges from 61.1 mA/℃ to 101.2 mA/℃ under load current from 50A to 80A. Besides, the linear sensitivity of pre-turn-off current is influenced by junction temperature and working conditions like, load current and bus voltage.
Conclusions
A novel TSEP pre-turn-off current is proposed in this paper. Double pulse tests are performed to characterize the relationship between the pre-turn-off current with junction temperature, load current and bus voltage. The temperature sensitivity is linear and high enough to evaluate junction temperature compares with the existing TSEPs, confirming its feasibility in junction temperature estimation for high voltage IGBT modules.
Appendix (Figure, table, image…)

Fig. 1. The Extraction principle of pre-turn-off current and its change rule with junction temperature
 

IGBT,HVDC,Junction Temperature Monitoring,Pre-turn-off